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- JavaScript Numbers are represented as [IEEE 754 double-precision floats](http://steve.hollasch.net/cgindex/coding/ieeefloat.html). Unfortunately, this means they lose integer precision for values beyond +/- 2^^53. For projects that need to accurately handle 64-bit ints, such as [node-thrift](https://github.com/wadey/node-thrift), a performant, Number-like class is needed. Int64 is that class.
-
- Int64 instances look and feel much like JS-native Numbers. By way of example ...
- ```js
- // First, let's illustrate the problem ...
- > (0x123456789).toString(16)
- '123456789' // <- what we expect.
- > (0x123456789abcdef0).toString(16)
- '123456789abcdf00' // <- Ugh! JS doesn't do big ints. :(
-
- // So let's create a couple Int64s using the above values ...
-
- // Require, of course
- > Int64 = require('node-int64')
-
- // x's value is what we expect (the decimal value of 0x123456789)
- > x = new Int64(0x123456789)
- [Int64 value:4886718345 octets:00 00 00 01 23 45 67 89]
-
- // y's value is Infinity because it's outside the range of integer
- // precision. But that's okay - it's still useful because it's internal
- // representation (octets) is what we passed in
- > y = new Int64('123456789abcdef0')
- [Int64 value:Infinity octets:12 34 56 78 9a bc de f0]
-
- // Let's do some math. Int64's behave like Numbers. (Sorry, Int64 isn't
- // for doing 64-bit integer arithmetic (yet) - it's just for carrying
- // around int64 values
- > x + 1
- 4886718346
- > y + 1
- Infinity
-
- // Int64 string operations ...
- > 'value: ' + x
- 'value: 4886718345'
- > 'value: ' + y
- 'value: Infinity'
- > x.toString(2)
- '100100011010001010110011110001001'
- > y.toString(2)
- 'Infinity'
-
- // Use JS's isFinite() method to see if the Int64 value is in the
- // integer-precise range of JS values
- > isFinite(x)
- true
- > isFinite(y)
- false
-
- // Get an octet string representation. (Yay, y is what we put in!)
- > x.toOctetString()
- '0000000123456789'
- > y.toOctetString()
- '123456789abcdef0'
-
- // Finally, some other ways to create Int64s ...
-
- // Pass hi/lo words
- > new Int64(0x12345678, 0x9abcdef0)
- [Int64 value:Infinity octets:12 34 56 78 9a bc de f0]
-
- // Pass a Buffer
- > new Int64(new Buffer([0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0]))
- [Int64 value:Infinity octets:12 34 56 78 9a bc de f0]
-
- // Pass a Buffer and offset
- > new Int64(new Buffer([0,0,0,0,0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0]), 4)
- [Int64 value:Infinity octets:12 34 56 78 9a bc de f0]
-
- // Pull out into a buffer
- > new Int64(new Buffer([0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0])).toBuffer()
- <Buffer 12 34 56 78 9a bc de f0>
-
- // Or copy into an existing one (at an offset)
- > var buf = new Buffer(1024);
- > new Int64(new Buffer([0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0])).copy(buf, 512);
- ```
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